Overshooting by convective settling

Abstract

We study a process of slow mixing in stars with convective envelopes, which is driven by the settling of cool downward plumes below the base of the convection zone. If a small fraction (of order $10^{-7}$) of the material cooled at the surface retains a significant entropy deficit while descending in plumes, it can reach the depth where lithium burning takes place. The model calculates the thermal response and mixing below the convection zone due to the settling process, assuming that the plumes arrive at the base of the convection zone with a broad range of entropy contrasts. We obtain a good fit to the observed lithium depletion in the Sun by assuming that the settling mass flux is distributed with respect to the entropy contrast as a power law with a slope around -2. We find convective settling to have a negligible influence on the stratification below the convection zone, although mixing induced by it could modify the gradient of helium concentration.

8 pages, 4 figures, accepted for publication in A&A

References in corpus (3)

• A more realistic representation of overshoot at the base of the solar convective envelope as seen by helioseismology
• Numerical Simulations of Penetration and Overshoot in the Sun
• How to define the boundaries of a convective zone and how extended is overshooting?

Cited by in corpus (8)

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• A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations
• Convective settling in main sequence stars: Li and Be depletion
• Addressing the acoustic tachocline anomaly and the lithium depletion problem at the same time
• Testing a non-local 1-equation turbulent convection model: A solar model
• Overshooting by differential heating